Subject: [HM] Calendrical questions
From: John Dawson (jwd7@psu.edu)
Date: Sun Jan 30 2000 - 15:21:55 EST
(1) Forgive me if this question has already been discussedd on this list;
if so I missed it, and it seems timely to bring it up. As we all know, on
the 29th of February we will experience a once-in-400-years event: the
addition of a leap day in a century year. That century years are not leap
years unless divisible by 400 is a correction called metemptosis (as I
learned some 5 years ago from a post of John Conway to another history
list), and many sources, including a recently published book on calendrical
calculations that I examined at the AMS meeting last week in Washington,
claim that that correction is the *only* difference between the Julian and
Gregorian calendars. But Conway's post mentioned another correction, called
proemptosis, that occurs in a century year usually once every 300 years,
but every eighth time at an interval of 400 years. Conway gave a formula
for determining in which years proemptosis occurs, but did not specify
precisely what the correction *is*. Is it also the addition (or perhaps
subtraction) of a single day? If so, which day? In particular, what
happens in years when both corrections occur?
(2) I understand that the doctoral dissertation of Abraham Fraenkel, the
well-known set theorist, concerned a method for computing the date of
Passover (presumably an improvement over the methods in use before). Has
his method been published, and is it still the preferred one?
Thanks to any and all who can provide enlightenment on these matters.
Dr. John W. Dawson, Jr.
Professor of Mathematics
Penn State York
1031 Edgecomb Avenue
York, PA 17403 U.S.A.
Tel.: 717-771-4131 (work)
717-846-1225 (home)
FAX: 717-771-8404
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